WINSTON-SALEM, N.C. -- Researchers at Wake Forest University School of Medicine will test whether an extract from the leaves of the ginkgo tree can slow memory loss in older adults.
They will ask participants in a large continuing national study -- the Cardiovascular Health Study (CHS) -- to sign up for the clinical trial of ginkgo. CHS is an observational study of cardiovascular diseases in 5,888 adults over 65 that has been underway since 1989 in Winston-Salem, Pittsburgh, Pa., Hagerstown, Md. and Sacramento, Calif.
Until now, no participants have received any treatment. The new six-year clinical trial will test whether 240 milligrams a day of ginkgo will slow memory loss, dementia and Alzheimer's disease.
The trial, paid for by the new National Center for Complementary and Alternative Medicine, is one of the agency's first to test a dietary supplement to see if it really works.
"Lots of people are already taking ginkgo biloba," said Gregory L. Burke, M.D., director of the clinical center at Wake Forest. "It's important for us to determine whether that's a good use of money and, more importantly, whether ginkgo biloba has a positive effect on memory. This issue needs to be resolved."
Burke, professor and interim chair of the Department of Public Health Sciences, said some German studies and several in the United States "suggest that ginkgo biloba may be an important way to reduce the burden of memory loss in older adults."
But those studies have been inconclusive. "That's why we're doing the trial." CHS was selected for the ginkgo trial "because we have previously collected information about memory function on our participants and how that has changed over time," said Curt D. Furberg, M.D., Ph.D., head of the new study's national clinical coordinating center. "It's a strength to have a population that is so well characterized."
All of CHS participants have been given annual tests of cognitive function and memory loss since the study began in 1989. In addition, most of the participants had a magnetic resonance imaging (MRI) exam .
The CHS study leaders have looked at a number of factors that could be related to memory loss, such as high blood pressure and certain cholesterol factors.
Furberg, professor of public health sciences, said that beginning some time next year, the clinical trial would enroll participants at all four CHS sites.
While it is possible that enough CHS participants will enroll to meet the goal of 2,000 participants nationally, Furberg and Burke expect that the trial may need to be opened to as many as 500 outside participants -- 125 at each center.
The participants in the trial will be randomized to one of two arms: they will either get 240 milligrams of ginkgo daily, or an inert placebo that looks the same. The participants will be closely watched for any side effects. They'll return for clinic visits at one month, four months, and then every four months over the six-year course of the trial.
Furberg noted that the 240 milligrams is "an optimal and safe daily dose." Added Burke, "There will be an independent monitoring board that will evaluate to make sure that people consuming ginkgo are not at increased risk."
If ginkgo has a dramatic effect in preventing memory loss, the trial could be stopped early. "Then all the participants will be informed and will be advised that taking ginkgo may be a good thing for them to do," Burke said.
Among the issues that still need to be resolved before the trial can begin is the precise source of the ginkgo, and how the tablets can be standardized.
The clinical trial will cost about $15 million nationally. Of that, $3.7 million is budgeted for the Wake Forest clinical center and the clinical coordinating center.